Pyrethroids, including both the naturally occurring compounds and their synthetically prepared analogs effectively control a variety of pests, such as ticks, mites, cockroaches, houseflies, mosquitoes, black flies, fleas, and other flying or crawling insects. They exhibit repellent as well as knockdown and kill activity against insects. Pyrethroids are not harmful to plants, food, animals or humans, and leave no harmful residues. Therefore, they are allowed to be applied on clothes in all countries. Despite these highly favorable characteristics, pyrethroid has had only limited general utility on cloth because of its relatively short-lived insecticidal action. This is due to the poor washing fastness of common finishing formulas, and decomposition of pyrethroid into a nonactive, noninsecticidal product in the presence of oxygen and ultraviolet light.
To prior inventions, U.S. Pat. No. 5,198,287 to Samson, et al. discusses a tent fabric with a water repellent and flame retardant coating that includes the insecticide permethrin. U.S. Pat. No. 5,252,387 to Samson teaches that permethrin can be preserved in insect repellent fabrics by placing a barrier over the permethrin. However, a problem with the prior art is retaining permethrin in washable garments through successive wash cycles.
U.S. Pat. No. 5,089,298 to McNally teaches that permethrin can be retained in garments impregnated with permethrin and amylopectin, a water insoluble form of starch, through a substantially greater number of laundering cycles than garments treated only with permethrin.
Whitcomb, U.S. Pat. No. 4,130,450 describes an insecticide-impregnated, open, low-density web that provides an expanded surface that may be loaded with contact insecticides, including pyrethrum and synthetically prepared insecticides. Whitcomb prefers the use of micro-encapsulated pyrethrum to avoid pyrethrum instability when exposed to ultraviolet light and oxygen. Whitcomb mentions that the web may be hung to permit vaporization of the active ingredient to combat flies.
Ronning et al., U.S. Pat. No. 4,765,982 is an example of the use of micro-encapsulated active ingredients to achieve a sustained release insect control effect. Pyrethroids, either synthetic or “natural”, are cited as useful. The Ronning et al. insecticidal device may be hung in the open to achieve a repellent effect in a restricted locate to drive insects from a nest or the like.
The present invention addressed the deficiencies in the prior art by utilizing polymeric nanocapsules as opposed to binders and barriers, such nanocapsules having pyrethroid compounds for effectively prolonging the durability of insecticides, even after solar exposure and repeated launderings.